1. Field of the Invention
This invention relates to a stacking tray for stacking therein stimulable phosphor sheets one by one by sheet feeding with a feed mechanism such as feed rollers and sheet falling by sheet weight. This invention particularly relates to a stacking tray for stacking stimulable phosphor sheets in the aligned form at a predetermined position in the tray.
2. Description of the Prior Art
When certain kinds of phosphors are exposed to a radiation such as X-rays, .alpha.-rays, .beta.-rays, .gamma.-rays, cathode rays or ultraviolet rays, they store a part of the energy of the radiation. Then, when the phosphor which has been exposed to the radiation is exposed to stimulating rays such as visible light, light is emitted from the phosphor in proportion to the stored energy of the radiation. A phosphor exhibiting such properties is referred to as a stimulable phosphor.
As disclosed in U.S. Pat. Nos. 4,258,264, 4,276,473, 4,315,318 and 4,387,428, and Japanese Unexamined Patent Publication No. 56(1981)-11395, it has been proposed to use a stimulable phosphor in a radiation image recording and reproducing system. Specifically, a sheet comprising the stimulable phosphor is first exposed to a radiation passing through an object to have a radiation image stored therein, and is then scanned with stimulating rays which cause it to emit light in proportion to the radiation energy stored. The light emitted from the stimulable phosphor sheet when the sheet is exposed to the stimulating rays is photoelectrically detected and converted to an electric image signal, which is processed as desired to reproduce a visible image having an improved quality, particularly a high diagnostic efficiency and accuracy. The finally obtained visible image may be reproduced in the form of a hard copy or may be displayed on a cathode ray tube (CRT). In this radiation image recording and reproducing system, the stimulable phosphor sheet is used to temporarily store the radiation image in order to reproduce the final visible image therefrom in a final recording medium. For economy, therefore, it is desirable that the stimulable phosphor sheet be used repeatedly.
In order to use the stimulable phosphor sheets repeatedly, after the image read-out by scanning with stimulating rays the stimulable phosphor sheet is subjected to the erasing of radiation energy remaining on the sheet, i.e. residual image erasing. The residual image erasing is conducted, for example, by exposing the whole surface of the stimulable phosphor sheet to light having a wavelength within the stimulation wavelength range of the stimulable phosphor constituting the sheet, or by heating the sheet. After the stimulable phosphor sheet is subjected to residual image erasing, the sheet is reused for image recording. In this process, the erased stimulable phosphor sheets are stacked in a sheet stacking tray and carried in this form to an image recording section. In this case, the stimulable phosphor sheets are stacked one by one in the stacking tray by sheet feeding with a feed mechanism such as feed rollers positioned in the vicinity of the upper section of the stacking tray and sheet falling by sheet weight. In order to guide the stimulable phosphor sheets securely into the stacking tray, the width of the feed mechanism is made larger than the width of the stimulable phosphor sheet, and the width of the stacking tray is made larger than the width of the feed mechanism. Therefore, the stimulable phosphor sheets guided into the stacking tray by the feed mechanism and falling thereinto by sheet weight do not always align at a predetermined position within the stacking tray, and are stacked in a form deviating from each other in the width direction of the sheets. Further, the sheets readily move inside of the stacking tray. As a result, the stimulable phosphor sheets move inside of the stacking tray during conveyance and are damaged. Also, when image recording is conducted on the stimulable phosphor sheet, the stimulable phosphor sheets are taken one by one out of the stacking tray by a member on the side of the image recording apparatus and are conveyed automatically to the image recording position. If the stimulable phosphor sheets do not align at the predetermined position inside of the stacking tray conveyed to the recording section, sheet deviation is caused at the image recording position by the sheet deviation in the stacking tray, and the sheet projects out of a predetermined image recording frame.